Intelligent wells include downhole remote flow-control devices used to open, close or regulate flow from and to multiple zones without the need for well intervention. Furthermore, intelligent wells are usually complemented by downhole permanent monitoring systems which provide valuable information used in the decision making process for the control of production or injection. All these systems require multiple control lines and cables to link the downhole tools to the associated surface equipment which serves as the interface between the operator and the system.
Current types of intelligent well systems in the industry include all electric, electro-hydraulic and all hydraulic systems. Most of the intelligent wells installed to date utilize hydraulic systems. Reasons for this preference for all hydraulic systems include lower costs, less complexity, perceived higher reliability and faster delivery times.
In hydraulic systems, the flow control devices can be either on/off or multi-position valves and can have either balanced piston or spring return type actuators. On the balanced piston design, two control lines are used for the operation of each valve, with each control line ported to either side of the piston (“open” and “close” ports). Applying hydraulic fluid pressure on one control line while the other is vented moves the valve in one direction with movement of the valve in an opposite direction accomplished by inverting the operation. On the spring return design, the valve operates with only one control line. Applying pressure to the single control line moves the valve in one direction, and, when this pressure is bled off, a mechanical or pneumatic spring moves the valve in the opposite direction.
Therefore, a need exists for multiplexed hydraulic control for operation of tools in a wellbore.